A/D Converter Voltage Range Control for Temperature-Varying Signals
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Solution Overview
Problem
AD converters struggle to accurately quantify signals from temperature-sensitive MEMS microphones, as constant full-scale voltage leads to increased signal amplitude with temperature changes, resulting in reduced quantization accuracy.
Innovation Solution
A signal processing circuit with an AD converter and a setting circuit that adjusts the voltage range dynamically based on temperature changes, with the setting circuit increasing the range when the signal amplitude increases and decreasing it when the amplitude decreases, using a reference voltage circuit that generates a reference voltage with a positive temperature coefficient to adjust the full-scale voltage accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the full-scale voltage is kept constant in the AD converter, then the reference voltage stability is maintained, but the quantization accuracy deteriorates when the input signal amplitude changes with temperature
Solution Approach 1:
The patent applies the dynamics principle by making the full-scale voltage dynamic rather than fixed. The setting circuit adjusts the full-scale voltage based on temperature changes, allowing the AD converter to adapt its quantization range to match the varying signal amplitude from the MEMS microphone, thereby maintaining quantization accuracy across different temperatures while the reference voltage itself remains stable.
Solution Approach 2:
The patent changes the parameter of full-scale voltage based on temperature conditions. When temperature increases and causes the MEMS microphone signal amplitude to increase, the setting circuit increases the full-scale voltage accordingly. This parameter adjustment ensures that the signal remains within the optimal quantization range, preventing saturation and maintaining measurement precision despite temperature variations.
2Measurement precision
If the full-scale voltage is increased to accommodate higher signal amplitude at elevated temperatures, then the quantization accuracy is maintained, but the signal-to-noise ratio deteriorates at lower temperatures
Solution Approach 1:
The setting circuit dynamically adjusts the full-scale voltage based on temperature conditions. At lower temperatures where the MEMS microphone signal amplitude is reduced, the circuit decreases the full-scale voltage to match the smaller signal range. This dynamic adjustment prevents the signal from being overwhelmed by quantization noise, thereby maintaining an optimal signal-to-noise ratio across the full temperature operating range.
Solution Approach 2:
The patent implements parameter changes by adjusting the full-scale voltage according to temperature. When temperature decreases and the signal amplitude reduces, the full-scale voltage is proportionally reduced. This ensures that the quantization steps remain appropriately sized relative to the signal amplitude, preventing excessive quantization noise and maintaining signal-to-noise ratio across varying thermal conditions.
3Device complexity
If a fixed reference voltage is used in the AD converter, then the circuit complexity is reduced, but the adaptability to temperature variations deteriorates
Solution Approach 1:
The patent introduces a setting circuit as an intermediary component between the reference voltage source and the AD converter. This intermediary circuit monitors temperature changes and adjusts the full-scale voltage accordingly, enabling the system to adapt to temperature variations without requiring a completely complex temperature-compensated reference voltage source. The setting circuit acts as a buffer that provides adaptability while keeping the overall system complexity manageable.
Solution Approach 2:
The patent segments the voltage reference system into two independent parts: a stable reference voltage source and a dynamic setting circuit. The reference voltage itself remains fixed and simple, while the setting circuit handles the temperature adaptation function. This segmentation allows each component to be optimized independently - the reference voltage for stability and the setting circuit for adaptability - reducing overall system complexity compared to a fully integrated temperature-compensated reference source.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach ensures accurate quantization of input signals across varying temperatures by dynamically adjusting the voltage range, maintaining optimal signal processing even as temperature affects the signal amplitude.
Implementation Method 1
using a reference voltage circuit that generates a reference voltage with a positive temperature coefficient to adjust the full-scale voltage accordingly
Data Source
AI summary
A signal processing circuit includes: an AD converter configured to quantize an input signal, whose amplitude changes in accordance with temperature, within a set voltage range and convert the quantized input signal into a digital signal; and a setting circuit configured to set the voltage range so as to be wider when the input signal is greater in amplitude in accordance with the temperature and so as to be narrower when the input signal is smaller in amplitude in accordance with the temperature.